Anionic polymerization of isoprene by the complexes oligoisoprenyllithium/tertiary polyamines in cyclohexane: 3. Structural study of the polymers by 1H n.m.r. at 100 MHz

Dumas, Sylviane; Sledz, J.; Schué, François; Raynal, Serge; Bywater, S.; Worsfold, D. J.

doi:10.1016/0032-3861(83)90061-7

Cited by 13 publications

(15 citation statements)

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“…However, in either numerous quantum chemical studies of polydiene active centers (reviewed in Refs. 13, 15, 16, 25) or the spectral (UV, 1 H, 13 C NMR) study of active centers 9, 15–19, 21–25, no unequivocal proof of the fulfillment of these condition has been obtained. In general, only the close values of negative charges on C α and C γ atoms are recorded.…”

Section: Introductionmentioning

confidence: 99%

“…In the specific case of anionic polymerization, we deal with the reaction complex “living polyisoprene–isoprene molecule.” As a result of excitation, the reaction complex acquires a diradical character. However, in the extensive literature on the structure of active centers and the mechanism of isoprene and butadiene polymerization by organic lithium (sodium) compounds 7–25, the traditional view of the nature of the reaction complex dominates. The electronic configuration of the ground state S 0 is ascribed to it.…”

Section: Introductionmentioning

confidence: 99%

“…Studies of the synthesis of polyisoprene rubber 7 led to the rapid development of the theory of anionic polymerization 7–25, 33–35. The principal point of this theory is the assumption that the monomer is inserted into the polymer chain on the most polarized bond C − Met + of the active center.…”

Section: Introductionmentioning

confidence: 99%

“…Investigations of the 1,3‐diene monomers polymerization, carried out for many years with the aid of nuclear magnetic resonance (NMR), ultraviolet (UV), and infrared (IR) spectroscopy 9–24, made it possible to advance a hypothesis of the π‐allyllic structure of active centers responsible for the synthesis of stereoregular rubbers. In the case of isoprene polymerization by organic lithium and sodium compounds, the structure of active centers can be represented as follows: …”

Section: Introductionmentioning

confidence: 99%

“…The concepts of the π‐allylic structure of the active center have long been used 8–24 to explain the formation of 1,4‐ (4,1)‐( cis , trans )‐units in the polyisoprene chain in hydrocarbon solvents as a result of C α carbon atom attack by isoprene (Schemes Ib and IIb) and 1,2‐ (4,3)‐units as a result of C γ carbon atom attack (Schemes Ia, Ic, IIa, and IIc) in electron donor solvents 8–11, 13–24. In another formulation, this assertion means that the synthesis of vinyl 1,2‐ (4,3)‐units in the presence of electron donors (D) will take place if the C

_{−}^{γ}

Met + · D bond is stronger than the C

_{−}^{α}

Met + · D bond, or the inequality | q (C γ )| ≫ | q (C α )| should be fulfilled.…”

Section: Introductionmentioning

confidence: 99%

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Structure of charge‐transfer reaction complexes in anionic polymerization of isoprene: Quantum chemical calculations

Kalnin'sh

Podolsky

2005

Int J of Quantum Chemistry

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ABSTRACT:A new mechanism of isoprene anionic polymerization is proposed. Its central moment is thermal electronic excitation of a living polyisoprene-isoprene complex into the quasi-degenerate electronically excited state (S ⅐ T) 1 , which is of the charge (electron) transfer character. It is asserted that the probability of chemical bond formation is determined by the free valence index on carbon atoms and by the geometry of reacting complex in the excited state (S ⅐ T) 1 . Semi-empirical AM1 and ab initio 6-31G* quantum chemical calculations revealed low energies of triplet excited levels (Ͻ10 kcal/mole). Comparison of isoprene polymerization on free anions and on solvated ion pairs shows that both types of active centers produce vinyl 1,2 (4,3)-units. Free anions generate predominantly 1,2-units, whereas solvated ion pairs tend to form units with the 4,3-structure. Analysis of energies of excited isoprenyl lithium ϩ isoprene complexes shows that the formation of 1,4 (4,1)-cis-polyisoprene in an inert media is most preferable.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

_{−}^{γ}

Met + · D bond is stronger than the C

_{−}^{α}

Met + · D bond, or the inequality | q (C γ )| ≫ | q (C α )| should be fulfilled.…”

Section: Introductionmentioning

confidence: 99%

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Structure of charge‐transfer reaction complexes in anionic polymerization of isoprene: Quantum chemical calculations

Kalnin'sh

Podolsky

2005

Int J of Quantum Chemistry

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Isoprene Polymers

Senyek

2008

Encyclopedia of Polymer Science and Technology

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Isoprene was first isolated from the pyrolysis products of natural rubber. The first preparation of polyisoprene was reported in 1879. In 1950, the goal of preparing synthetic cis 1,4‐polyisoprene as a counter part to natural rubber was achieved. Attention was then focused on commercial preparation of isoprene for polymerization use. Shortly after the discovery of stereospecific catalysts, the first commercial polyisoprene plant came on stream in 1959–1960 using a lithium catalyst. Isoprene is a reactive diene that undergoes cycloaddition, electrophilic, nucleophilic, free‐radical, and coordinated catalytic addition, and thermal dimerization. Information on the production of isoprene by naphtha cracking as well as the synthetic processes is detailed. Depending on the catalyst and conditions, isoprene may undergo 1,2,3,4, or 1,4 addition leading to several isomeric structures. Coordination catalysts, alkali metal catalysts, and Alfin catalysts are important for polymerization and are discussed. Chemical modification of polymers is a convenient way of altering physical and mechanical properties. Highly unsaturated polymers such as polyisoprene are easily modified because the olefinic bond is readily available. Their high reactivity with a variety of chemical substances offers advantages in chemical modification and vulcanization. However, reaction with oxygen and ozone causes degradation and loss of physical and mechanical properties. Synthetic polyisoprene is processed on conventional rubber machinery. Compounding technology is similar to that used for natural rubber. Typical formulations are given. A brief discussion of isoprene copolymers and 1,4‐ trans ‐polyisoprene is included. Isoprene is classified as a flammable liquid. It is a moderate irritant to the skin, eyes, and mucous membranes. The primary use for cis ‐1,4‐polyisoprene is in tires and tire products. It is also used, eg, in molded and mechanical goods, adhesives, belts, foam rubber, and elastic threads.. Automotive molded products and medical applications are typical. Trans ‐1,4‐Poyisoprene can be extracted, calendered, injection molded, and compression molded. It can be used in blends with other polymers. Its main use is in golf ball covers.

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Synthetic Rubbers, Technical Production and Properties of

Asai¹

2001

Biopolymers Online

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Introduction History Isoprene Polyisoprene Other Copolymers Chemical Synthesis Isoprene cis ‐1,4 Polyisoprene trans ‐1,4 Polyisoprene 3,4 Polyisoprene Others Technical Production Isoprene Polyisoprene Others Properties Isoprene cis ‐1,4 Polyisoprene trans ‐1,4 Polyisoprene 3,4 Polyisoprene Others Outlook and Perspectives Isoprene cis ‐1,4 Polyisoprene trans ‐1,4 Polyisoprene 3,4 Polyisoprene SBIR Others Relevant Patents

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Anionic polymerization of isoprene by the complexes oligoisoprenyllithium/tertiary polyamines in cyclohexane: 3. Structural study of the polymers by 1H n.m.r. at 100 MHz

Cited by 13 publications

References 3 publications

Structure of charge‐transfer reaction complexes in anionic polymerization of isoprene: Quantum chemical calculations

Structure of charge‐transfer reaction complexes in anionic polymerization of isoprene: Quantum chemical calculations

Isoprene Polymers

Synthetic Rubbers, Technical Production and Properties of

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